davies



Feb. 16, 1960 R. J. DAVIES 2,925,460

ELECTRIC CONNECTOR Filed Sept. 23, 1954 as 32 I I w 7 W 10 x z zT T INVENTOR. RICHARD J. DAVIES m amd Afforneys United States Patent ELECTRIC CONNECTOR Richard J. Davies, Afton, N.Y., assignor to Bendix Aviation Corporation, Sidney, N.Y., a corporation of Delaware Application September 23, 1954, Serial No. 457,809

17 Claims. (Cl. 174-77) This invention relates to electrical apparatus and more particularly to means for maintaining the terminal ends of electrical conductors in operative engagement.

One of the objects of the present invention is to provide novel apparatus for effecting a readily separable radioshielded connection of electrical conductors.

Another object of the invention is to provide novel means for insuring good electrical contact of electrical conductors and the insulation thereof from surrounding parts.

Still another object is to provide novel means in electrical connectors for effectively preventing flashovers between high potential conductors'and parts which are at a lower or ground potential.

A further object is to provide novel means for operatively joining insulating tubes within detach-ably connected conduits surrounding said tubes.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. l is a side elevation, with parts broken away and partly in section, of a radio shielded spark plug and terminal connection therefor, the section being taken substantially on line 11-of Fig. 2;

Fig. 2 is a detail plan view of the spring retaining sleeve of the device-of Fig. l; and,

Figs. 3 and 4 are views corresponding to Figs. 1 and 2, respectively, and showing a modification.

Two embodiments of the present invention are illustrated in the drawings, by way of example, in the form of a connector for connecting a radio-shielded conductor of high potential electrical energy to the input terminal of a radio-shielded spark plug in the ignition system of an internal combustion engine. It will be understood, however, that the invention is adaptable in many other environments in the electrical art.

In the form shown in Fig. 1, the spark plug is of the type comprising a shell 11 adapted to be threaded into the cylinder of an engine. Mounted in shell 11 in any suitable known manner is a tubular insulator 12 which supports a center electrode 14 and insulates .it from the shell. The upper or outer end of insulator 12 has an enlarged bore forming a recess 15 at the inner end of which is the terminal 16 of the center electrode.

The parts 14, 16 herein called a center electrode and terp which serves as a radio-shielding element and is normally at ground potential. The upper or outer end of barrel17 preferably extends beyond the end of the insulator and electrode 14.

2,925,460 Patented Feb. 16, 1960 is externally threaded for cooperation with a tubular, internally threaded nut 18 whereby the barrel is operatively connected with a metallic conduit 19 to effect a continuous metallic enclosure for an electrical conductor. As shown the conduit 19 comprises a flexible tube or conduit 20 having a rigid fitting or ferrule 21 soldered or otherwise suitably secured to the end thereof. Nut 18 has an internal flange or shoulder 22 which engages an external shoulder 23 on the ferrule, whereby the latter and barrel 17 are held in firm end-to-end engagement when the nut is screwed home on the barrel. This construction insures complete radio shielding and good electrical contact between the associated elements. For a purpose to hereinafter appear, the lower end of ferrule 21 is provided with an internal flange 24.

Extending from conduit 19 into recess 15 is an electrical conductor 26 surrounded by the usual insulation 27. The lower or free end of said conductor is provided in any suitable manner with a compressible resilient terminal 28 which engages spark plug terminal 16 to effect an electrical connection between conductor 26 and center In the illustrated embodiment, spring 28 is supported on a nut 35 by having one turn thereof in an annular groove in the nut. The latter threadedly engages a tip piece 36 soldered or crimped onto the end of conductor 26.

In order to minimize the danger of flash-overs or sparking between terminal 28 and barrel 17, there is provided an insulating sleeve 29 which preferably has a close fit around the insulated conductor 26, 27 and is preferably made, at least in part, of a flexible material, such as synthetic rubber. As illustrated, said sleeve consists of three integral flexible portions; an enlarged cylindrical portion 30 which preferably has a close fit in recess 15 of insulator 12, a reduced upper portion 31, and a flange portion 32 having a lower plane face 33 engaging the upper end of insulator 12 and an upper bevelled face 34.

In order to provide a firm engagement and tight seal at the engaging surfaces of flange 32 and insulator 12, 'novel simplified means are comprehended by this invention for applying a sufiiciently large yielding pressure to the upper face of the flange during the act of connecting the two units without the necessity of any detrimental movement of conductor 26, 27 relative to its conduit 19. Said means, in the form shown, comprises a sleeve 37 of metal or other suitable material loosely surrounding the cylindrical portion 31 of insulating sleeve 23. At the lower end of sleeve 37 is an external flange which is internally bevelled and engages the surface 34 of sleeve 29. The other end of sleeve 3'7 is of such size as to pass freely through ferrule flange 24 but is provided with novel means adapted to cooperate with said flange for retaining the end portion of the sleeve within the ferrule and for limiting the relative axial movement of the sleeve and ferrule. Said means, in the form shown in Figs. 1 and 2, comprises a plurality of resiiient ears 3% which spring outwardly after passing through the opening provided by flange 24 and engage the upper surface of said flange. Thus, the axial movement of the sleeve 37 is limited in one direction by internal flange 24 and in the other direction by a flange 40 in ferrule 21. The ears 39 may be formed, as shown, by shearing the wall of sleeve 37 for short distances axially and circumferentially and bending portions of said wall outwardly. If the material from which sleeve 37 is made is not resilient, the resilient ears 39 may be secured thereto by any suitable known means, such as by riveting.

To provide the yielding pressure for pressing sleeve flange 32 against the end of insulator 12, a coil spring mined initial compression with ears 39 engaging flange 24. In one successful embodiment of the invention, in apparatus like that illustrated, the spring was initially compressed a distance of about one eighth of an inch.

The above described parts are so proportioned that .when conduits 19 and 17 are being attached by threadpressure thus applied will be the sum of the initial compression of spring 41 and the additional compression thus efiected during assembly. This substantial pressure against flange 32 is obtained with only a small and inconsequential movement of the conduit 19 relative to the cable 26, 27. This relative movement is measured by the distance between flange 24 and cars 39 when the parts are fully assembled as in Fig. l.

The embodiment of Figs. 3 and 4 is the same as that of Fig. 1 except for the formation of the retaining ears on the spring retaining sleeve 42. The cars 43 on the latter are punched out sections of the sleeve wall and face downwardly. When sleeve 42 is being installed in the ferrule 21, ears 43 bend inwardly as they pass flange 24 and then return to locking or holding position above the In one commercial embodiment of a'spark plug and shielded lead of the type illustrated, the spring 41 is initially compressed a distance of one-eighth of an inch. During final assembly, said spring 'is compressed an additional one-sixteenth of an inch. Thus, for applying a predetermined given pressure to flange 32, the present invention requires a movement only one-third as great as that required of comparable prior art devices of comparable simplicity.

Although only a limited number of embodiments or modifications of the invention are illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, the same type of joint or connection may be used at the ignition harness manifold end of a spark plug lead. as well as in many other environments. The surface 34 need not be bevelled and the ears or fingers 39 and 43 may be fewer or greater in number. The spring fingers or cars 39 need not be at the end of sleeve 37 but may be at some 7 intermediate level, as are the cars 43 in Fig. 3. In some embodiments, the surface 33 may engage a shoulder or flange on an insulator instead of the end thereof,as illustrated, or in some installations surface 23 may engage 'a shoulder or flange which is integral with the spark plug barrel or equivalent conduit. Various other changes may also be made in the design and arrangement of parts illustrated as well as in the materials suggested without departing from the spirit and scope of theinvention, as

thesame will now be understood by those skilled in the art , What is claimed is: a 1. 'An electrical lead adapted for use in combination with a member having an insulator fixed therein, said lead comprising a conduit, means for detachably connectpressible by movement of said conduit into engagement with said member after said sleeve and insulator are engaged.

2. An electrical lead as defined in claim 1 wherein said resilient means comprises a coil spring. 7 3. An electrical lead as defined in claim 1 wherein said resilient means is maintained under compression to a predetermined extent between said conduit and enlargedportion of the element when said lead is detached from said member and said conduit and element are extended to the full extent permitted by said limited axial movement.

4. An electrical lead as defined in claim 3 wherein said resilient means is further compressed when said lead is attached to said member with the conduit and member in end-to-end engagement.

5. An electrical lead as defined in claim 1 wherein said element is a tubular sleeve slidably extending into of said element relative to said conduit when the conduit is detached from said member and compressible resilient means interposed between said conduit and an enlarged 8. In apparatus of the class described, a conduit having 7 a shoulder therein, a tubular sleeve having one end portion extending into said conduit and the other'end portion of the sleeve beingoutside of said conduit, said otherend portion having external flange means thereon, at least one resilient finger on said one end portion, said finger being yieldable to permit insertion of said one end portion into said conduit past saidshoulder and engageable, when unbiased within the conduit, with said shoulder to limit the movement of said sleeveout of said conduit, and resilient.meansinterposed under compression between said conduit and flange means.

9. Apparatus as defined in claim 8 wherein each said resilient finger is an integral part of said sleeve.

10. Apparatus as defined in claim 8 wherein each said resilient finger is secured at one end to' said sleeve and extends in a circumferential direction around the sleeve.

11. Apparatus as defined in claim 8 wherein each said resilient finger is secured at one end to said sleeve and extends longitudinally thereof.

in an end portion thereof, a tubular element operatively engageable with said member and conduit for releasably connecting the same togetehr in end-to-end relation, an insulating sleeve, and means for 'yieldably pressing sald l sleeve againstsaid insulator including a second sleeve having one end portion thereof extending into said conduit and the other end portion thereof engaging said insulating sleeve, means on said second sleeve engageable with said shoulder for limiting the movement of said second sleeve out of said conduit, flange means on said other end 'portion of said second sleeve and resilient means interposed under compression between said flange means and said conduit when the latter and said second sleeve are fully extended. i

' 14. An electrical lead adapted for use in combination with a recessed member, an insulator 'in said recess, a terminal'in said insulator, and means for detachably connecting said member and lead, said lead comprising a conduit having a shoulder in an end portion thereof, a conductor extending from said conduit for electrical engagement with said terminal, an insulating sleeve surrounding t e projecting end portion of said conductor for engagement with said insulator, and means rendered operative by said connecting means for pressing said insulating sleeve against said insulator including a tubular element projecting into the conduit and having means adjacent one end thereof engageable with said shoulder to limit movement of said element out of said conduit and resilient means interposed between said conduit and flange means on the other end portion of said element, said resilient means being under compression when the conduit and element are fully extended thereby.

15. In electrical apparatus, a tubular barrel, an insulator having a recess therein fixed in said barrel, an insulating sleeve having a portion extending into said recess and an annular surface engaging an annular surface of said insulator, said annular surfaces being transverse relative to the longitudinal axis of said sleeve, a nut having threaded engagement with said barrel, a conduit engage able by said nut to secure said barrel and conduit together in end-to-end engagement, a tubular element extending into said conduit, means on said conduit and element for limiting movement of the element out of the conduit, said element having an enlarged portion outside of said conduit and being engageable with said insulating sleeve, and resilient means interposed between said conduit and said enlarged portion of the element, said resilient means being under compression when the conduit and element are fully extended and being further compressible during the final movement of said conduit into engagement with said barrel to apply pressure to said annular surfaces.

16. In electrical apparatus of the class described, two abutting conduits, the first of which has a shoulder in the end portion thereof, means for operatively connecting said conduits, an insulator fixed in the second conduit and having a terminal therein, a conductor extending from said first conduit into electrical engagement with said terminal, an insulating sleeve surrounding said conductor and engageable with said insulator, and means operable by said conduit connecting means for pressing said sleeve against the insulator including a tubular element extending into the end of said first conduit and having means thereon engageable with said shoulder for limiting the movement of said element out of said first conduit and resilient means interposed between said first conduit and flange means on said element, said resilient means being under initial compression when the conduits are detached and being further compressible by said conduit connecting means while the conduits are being connected.

17. In apparatus of the class described, in combination, a spark plug including a central electrode and a shielding shell and having insulation therebetween, a shielded current conducting cable terminating in a connector projecting from its shield and adapted to contact the spark plug within the confines of the shell insulator, an insulating sleeve covering said conducting cable Within the spark plug shell, said sleeve being flanged to seal against the shell insulator and extending into the cable shield, means to connect the cable shield and spark plug shell, a hollow, tubular element disposed over said sleeve and extending between the flange thereon and the cable shield and telescopic within the shield, said tubular element having means thereon for cooperating with said shield to retain said element in telescopic relation with the shield, and a compression spring pro-loaded between said element and the cable shield and further compressible between said element and the cable shield.

References Cited in the file of this patent UNITED STATES PATENTS 2,038,778 Williams Apr. 28, 1936 2,684,398 Strunk July 20, 1954 2,759,040 Knudson Apr. 14, 1956 2,759,989 Anderson Aug. 21, 1956 

